Hereditary or “predisposition” genetic testing looks for specific inherited changes (mutations) in a person’s genetic make-up. Genetic mutations can have harmful, beneficial, neutral, or uncertain effects on health. Mutations that are harmful may increase a person’s chance, or risk, of developing a disease such as cancer. Overall, inherited mutations are thought to play a role in 5-10% of all cancers. These particular disease states are known as hereditary cancers, and proper genetic testing can be used to determine an individual’s risk.
Cancer is a disorder in which normal control of cell growth is lost—causing abnormal proliferation of the effected cells. Inherited genetic mutations can increase a person’s risk of developing cancer through a variety of mechanisms, depending on the function of the mutated gene. Mutations in genes that control the repair of damaged DNA and cell growth are particularly likely to be associated with an increased risk of cancer.
Some people inherit mutation(s) in the germline, potentially allowing for the cancers associated with the mutation(s) to be passed on. These mutation(s) occur in two classes of cellular genes: oncogenes and tumor suppressor genes.
Cancer can sometimes appear to “run in families” even if it is not caused by an inherited mutation. For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns, such as the types of cancer that develop, other non-cancer conditions/symptoms that are present, and the ages at which cancers develop, may suggest the cancer is in-fact hereditary in nature and due to inherited genetic mutation(s).
Advancements in gene sequencing technologies have allowed for genetic mutations that cause many hereditary cancers to be well described, and sophisticated mutation screening can confirm whether a cancer is, indeed, the result of an inherited mutation. Genetic testing is also performed to determine whether asymptomatic individuals with family members effected by cancer have inherited the causal genetic mutation.
- Often, multiple genetic mutations in a single individual are responsible for the development of hereditary cancers.
- Advantages of cancer gene panels include decreased cost and improved efficiency of cancer testing by decreasing the time involved, number of patient visits, and number of tests sent.
- A negative genetic test is more reassuring at eliminating the likelihood of inherited risk when all known genes of that phenotype have been assayed.